Integrated circuit devices are being fabricated with decreasing transistor geometry sizes that result in increased leakage currents during operation thereof. One solution to reducing leakage currents when operation of the integrated circuit device is not required is to shut down and/or remove power from some or most of the transistor logic circuits of the integrated circuit device. This puts most of the transistor logic circuits of the integrated circuit device into a “low power consumption mode,” e.g., a “deep sleep mode,” that substantially reduces the power consumption of the integrated circuit device during extended standby conditions that may be defined through software and/or firmware.
For example, the low power consumption (deep sleep) mode may shut down a majority of the circuits in the integrated circuit device while still maintaining logic level values at both internal and external connectivity points of the integrated circuit device, e.g., through keeper cells. The keeper cells may be used to retain, e.g., “keep,” the logic levels of the external input-output (I/O), internal status, configuration, and/or enable signals that were present just before the integrated circuit device went into the deep sleep mode. Due to the nature of what the deep sleep mode does to the circuits of the integrated circuit device, entry into and exit from the deep sleep mode must be as robust as possible.
Therefore, it is very likely that a hardware fault in the configuration inputs for the deep sleep mode may cause the integrated circuit device to enter into a state from which it may never be able to wake up. This inability to wake up would effectively lock-up (hang-up) the integrated circuit device so that it could never recover from and come out of the deep sleep mode. Robustness of an exit from the deep sleep mode may be accomplished through the use of a deep sleep watchdog timer (DSWDT) and the like. However, what insures the robustness of the DSWDT or other exit function so that the integrated circuit device is not trapped in a deep sleep mode that is non-recoverable?